The invention relates to memory controller hubs.
Microcomputer systems generally include one or more memory controller hubs that control and coordinate the transfer of data between the computer""s system memory, central processing unit (CPU), and peripheral devices. Graphics applications may be supported by peripheral devices known as graphics controllers that require a memory controller hub to transfer data between the devices, the system memory, and the CPU.
A design concern associated with microcomputer systems is the quality of two-dimensional (2D), three-dimensional (3D), and video image (often collectively referred to below as xe2x80x9cgraphicsxe2x80x9d) processing. High-performance graphics processing requires processor-intensive calculations and the fast manipulation of large quantities of data. Several designs have been implemented to achieve high-performance graphics processing while also reducing the cost of the complete system and allowing for upgrades to the computer system""s capability.
A computer system may include a graphics controller coupled to local memory for storing graphics data, so that the amount of data that must be transferred between the graphics controller and the system memory and/or the CPU is reduced. Increasing the amount of local memory available to the graphics controller improves graphics performance, but also increases the cost of the computer system, since local graphics memory is relatively expensive. Less local memory is required to achieve the same graphics performance, however, if a dedicated bus, e.g., an Accelerated Graphics Port (AGP), is used to couple the controller to the memory controller. An AGP allows the controller to treat portions of system memory as dedicated local graphics memory, which reduces the amount of local memory required and lowers overall system costs.
Computer system costs may also be reduced by eliminating the peripheral graphics controller and integrating its functionality into the memory controller hub. In such a configuration the memory controller hub is better described as a graphics/memory controller hub (GMCH), since it performs graphics processing functions in addition to memory control and transfer functions. Additionally, it includes one or more output ports to send graphics signals to external devices, such as cathode ray tubes (CRTs) and flat-panel monitors. Local graphics memory may then be eliminated.